MANTARESEARCH.COM - MANTA ECOLOGY PROJECT

Origins of the Manta Ecology Project

I worked as a dive guide in the Maldives, taking guest divers to various sites including weekly visits to sites known as “Manta Points” which are established cleaning stations which the mantas visit in order to be cleaned of dead skin and parasites by a number of, typically, wrasse, species. I was unable to answer questions about whether the mantas were the same on each visit or whether they visited every week or how long they cleaned for. There was no information in readily available references nor from marine biologists I was in contact with. I developed a manta identification system based on website information from researchers in Yap, Japan and Australia that the markings on the ventral side of the manta were individual. There was no written method, nor other information specifically about how to use the markings so the first step was to develop a rigorous identification method. The method was honed over a period of around three months (December 01 to February 02) and has been used successfully for over 23 years now. The method can be used to identify all manta species and colour types (chevron” and “black”).

Contributions from a number of sources are included in the database. 

In September 2005 a special Microsoft Access database was developed and all the records were transferred to this. 

Mantas are very much part of the culture of the Maldives. There is no commercial fishery but many islands and reefs are named from local fishermen’s observations of mantas in the locality and it has been known a very long time that mantas are seen on the lee side of the atoll to the prevailing wind. The wind (monsoon) patterns are “North East”: November to April, and “South West”: May to October. Data collection has strongly supported the hypothesis that the mantas migrate from the east to the west side of the atolls with the movement of the plankton and the monsoon changes. Additionally we have a smaller proportion of mantas identified in different atolls, requiring them to traverse water minimum 350m deep and some gaps between the atolls are over 1500m deep. Reef mantas have been reported from the far north travelling to central atolls and far south to central. I can hypothesize that mantas may travel further south towards Chagos archipelago and north to Lakshadweep archipelago (India) and therefore across national borders where no protection occurs. To date no Maldives mantas have been reported elsewhere.

In addition to making records of mantas seen during regular tourist dives, extended observation as at the cleaning stations were performed in order to answer the following:

1. How long a manta spends cleaning in one day or cleaning period? (simple answer is 5-240+ minutes)

2. How many mantas visit a cleaning station in a day (period of daylight hours)? (over 110 recorded over a 10 hour observation window)

3. Which other fish are involved in the cleaning act and how many?

4. What are the effects of currents and tides on the presence of mantas?

They also provided excellent opportunities to observe and describe novel behaviour.

Behaviour

The only manta behaviour to have been previously described in detail is copulation.

A number of novel behaviours have been described from these observations.

1. Arriving. A manta arrives at the cleaning station and makes their presence known to other mantas by form of a formalised greeting. The mantas arrive to the cleaning station by swimming in from deep water and by swimming parallel to the reef for some distance, sometimes making several passes of the cleaning station before settling down and clean. Arriving may also encompass some demonstrating behaviour as a large manta may arrive with a group of mantas and then swim away leaving the other mantas to clean.

2. Greeting. If other mantas are already present at the cleaning station the arriving manta faces other mantas in cleaning circle and watches them to ascertain position in hierarchy. In some cases the manta will slip in behind all the other mantas once it has “greeted” them all and in some cases a “Head Off” will occur.

3. Cleaning circles (video link). Groups of 2+ mantas swim in tight circles over reef area where there is high concentration of cleaners. If there is significant current so the mantas have to swim into the current the circle will be replaced by a line and mantas take it in turns to swim to the front of the line, clean and the drop to the back and allow another to take their place. Mantas need to keep swimming to funnel water over their gills so they can continue to breathe. Swimming (or hovering) into a strong current serves the same purpose.